Rotary core drill



correct rate of advance of the cutters.

Patented Jan. 24, 1933 rss PATENT OFFICE GEORGE A. MACBEADY, 01 L08 ANGELEB, CALIFORNIA norm! cons Dam.

Application filed latch 14, 1929, Serial No. 848,958. Renewed October 12, 193:.

My invention relates to rotary core drills of the double barrel type in which the floating inner barrel is free to rotate relative to thecuter barrel.

In this type of core drill the function of fioatin inner barrel is to move longitud1- nally without rotatin over a core cut by rotary cutters attache to and driven by the outer barrel. In firm homogenous formation this t e of core drill functions very satisfactor' y but in the soft unconsolidated formations common in oilfields it does not always function so satisfactorily and cores are often broken or twisted at short intervals. For the purpose of orienting cores to determine the direction of stratigraphic dip in rotary drilled holes it is desirable to obtain long unbroken segments of core.

One of the causes for difficulty in obtaining long unbroken cores of soft material is the uncertainty of knowing and maintaining the fed too rapidly cuttings accumulate to lock the two barrels together but if fed too slowly the cutters out until the ipe is hanging and in most forms of core drills there is no pressure remainin to hold the floating inner barrel centere over its core with the result of a broken core.

An object of my invention is to hold the floating inner core barrel on its core with uniform pressure in spite of minor variations in rate of advance of cutters, speed of cutting, or hardness of formation: and to accomplish this I make use of a compressed sprin coupled in the floating inner core barre member.

With the foregoing and other objects in view which will be made manifest in the following detailed description and especially inted out in the appended claims, reference 1s had to the accompanying drawing for il lustrative embodiment of my invention, wherein: V

Figure 1 is a side elevation of a core drill with the middle portion of the outer barrel broken away to show the spring coupling and other novel features of my invention:

Figure 2 is a longitudinal section of the spring coupling on a larger scale than Figure 1 an Figure 3 is a cross section at ;33 on 'Rotatably mounted within the outer barrel 2 is the inner core barrel member, designated in general as 3, provided with a cutting nose 4 at the lower end thereof, and a thrust bearing 5 at the upper end thereof.

The function of the thrust bearing 5 is to transmit thrust caused by the weight of the drill pipe to the inner core barrel member 3 to force it longitudinally over a core and at the same time to reduce the rotational friction so that the rotating outer barrel 2 will 79 not cause the inner barrel 3 to rotate. The thrust bearing 5 can be a ball bearing, a roller bearing, a point bearing, a journal bearing, or any other type of thrust bearin used in core drills. The inner core barre 7 member 3 includes a core receiving tube 20 provided with a core retainer not shown and a check valve 21 of any form commonly used in core drills in addition to the sprin coupling designated in general as 6 whic is a novel feature of this invention. The details of the spring coupling 6 are as follows. The coupling 7 is connected to the top of the inner core barrel member 3 preferably by screw threaded attachment to the check valve 21. Attached to coupling 7 is a shaft 8 of smallerdiameter so that a shoulder 9 is formed at the joint which is preferably screw threaded. The opposite end of shaft 8 is provided with an enlargement 9 10 formin a shoulder 11. A sleeve 12 is mounted a out the shaft 8 in such a manner as to provide a close but freely sliding fit and is provided with an end 13 facing the shoulder 9 and with an internal shoulder or end 14; to engage shoulder 11 of the shaft 8; Of course sleeve 12 is of suflicient length and accuracy to preserve the alignment of the inner core barrel member 3. Means are provided for attachment to a tube 18 within tionable.

which the enlargement 10 may slide, such as the internally threaded apron 15.

Optionall relative rotation between sleeve 12 and shafl. 8 can be prevented by use of a key 17 imbedded in keyways. Under some conditions relative rotation is not desirable while under other conditions it is not objec- Tube 18 is attached to thrust bearing 5 by threaded cou ling or otherwise. Shims 19 ma be provide to adjust the length of the space between end 13 and shoulder 9.

A compression spring 16 is mounted about the shaft 8 between the end 13 of sleeve 12 and the shoulder 9 of coupling 7. S ring 16 can be a coil spring as shown in the rawmg, a disc spring, or any other form of compression spring and the dimensions can be varied to suit the hardness of formation cored by selection of size of sprin When spring coupling 6 is assembled t e sprin 16 may be partially compressed but not to its full limit of travel. For example: under one set of conditions usin a two inch diameter core receiving barrel used a sprin made of 15 coils of half inch round rod coi ed 1% inches inside diameter with lengths of 8% inches unloaded, 7 inches assembled in spring coupling, and 6% inches when compressed under full core load. These dimensions allowed the nose 4 to travel one inchlongitudinally relative to bit 1.

The functions and operation are as follows. The core drill is assembled as described and lowered to the bottom of the hole preparatory to coring. When bit 1 is rotated and lowered it cuts a core and nose 4 rests on the top of the core. As bit 1 is fed deeper, weight from the drill pipe is transmitted through thrust bearing 5 to sleeve 12. If the formation is very soft spring 16 may not compress and nose 4 will then be forced into the formation and over the core causing the core to enter the core receiving barrel: and the core is prevented shearing off by the nose 4 being imbedded in the formation ahead of the bit 1. If the formation is hard spring 16 compresses allowin nose 4 to retreat behind the cutting edges 0% bit 1 until the pressure is suflicient to force the nose over the core: furthermore as the nose retreats behind the cutting edges of the bit the flanks of the core are relieved to permit shavings to escape laterally instead of being pushed into the rock matrix as is necessary when the nose is in soft formation ahead of the bit.

When there are changes in hardness of formation or speed of descent of bit the spring 16 adjusts the nose 4 to its proper position and holds it on the core with steady pressure. This feature contrasts with a core drill not rovided with a spring when rotation is continued after ceasing to feed the rotary bit down. In the latter case the rotation of the bit soon digs hole until the bit hangs suspended instead of resting on the bottom of the masses hole and the inner barrel is also suspended so that even sli ht vibration of the core drill may cause s cient upward or lateral movement to break the core.

It will be understood that various changes in detail of construction may be made without departing from the spirit or scope of the invention as defined by the appended claims.

I claim as my invention:

1. A rotary core drill comprising an outer barrel, an inner barrel having a limited longitudinal movement relative to said outer barrel, a thrust bearing permitting relative rotation between said barrels, and a compres 810D. spri ada ted to transmit thrust between said arre the longitudinal travel of said spring being substantially equal to the ion 'tudinal movement between said inner an outer barrels.

2. In the inner barrel of a rotary core drill: a coupling comprising a mandril threaded at one end and provided with an enlar ement at the opposite end, a sleeve slidably disposed about said mandril having a bore of smaller diameter than the diameter of said enlargement for a portion of the length facing the thread end of said mandril and threaded at the opposite end for attachment in a core barrel, 9. coupling threadedly connected to the thread end of said mandril and provided with threads at the opposite end for attachment in a core barrel, a coil sprin disposed about said mandril between sai couplin and said sleeve, a key fitting in keyways 0 both mandril and sleeve adapted to prevent relative rotation therebetween, and shims adapted to ad'ust the length of space occupied by sai spring.

3. A rotary core drlll comprising an outer barrel, a rotary core cutting bit on the lower end of said outer barrel, a core receiving barrel within said outer barrel havin longitudinal movement relative t ereto and the lower end thereof adjacent said bit, a compression spring between the upper ends of said barrels havin a travel substantially equal in length to t e longitudinal movement between said barrels and compressible by longitudinal thrust between said barrels, and a thrust bearing adapted to transmit longitudinal thrust between said barrels and providing for relative rotation between said barrels when said 5 ring is compressed.

4. A rotary core diill com rising an outer barrel, a rotary core cutting hit on the lower end of said outer barrel, a core receiving barrel within said outer barrel havin a limited longitudinal movement'relativet ereto and the lower end thereof adjacent said bit, a compression spring between the upper ends of said barrels having a travel substantially equal in length to the longitudinal movement a limited between said barrels and compressible by londinal thrust between said barrels and roviding for relative rotation between said arrels when said spring is compressed, the lower end of said inner barrel normally r0 ecting ahead of the cutting edge of said it ut retractable behind said edge by compression of said spring.

In testimony whereof I have signed my name to this s cifieation.

- C ORGE A. MACREAD Y. 

